The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Combustion of an air/fuel mixture within a cylinder of an engine generates torque. A cylinder pressure sensor associated with the cylinder measures pressure within the cylinder. The cylinder pressure sensor generates a cylinder pressure signal based on the cylinder pressure. For example only, the cylinder pressure signal may include a voltage signal. The cylinder pressure sensor may transmit the cylinder pressure signal to a control module (e.g., an engine control module) via a first electrical conductor (e.g., wire).
The cylinder pressure sensor generates the cylinder pressure signal relative to a reference level. The reference level refers to the cylinder pressure signal from which the cylinder pressure signal increases as the cylinder pressure increases during combustion within the cylinder. Over time, however, operation of the cylinder pressure sensor causes the reference level to approach an upper limit of a predetermined range of the cylinder pressure signal. For example only, a filter/amplifier of the cylinder pressure sensor may wind up over time and cause the reference level to approach the upper limit.
The cylinder pressure signal may be clipped by the upper limit when the reference level approaches the upper limit. For example only, the cylinder pressure signal may be clipped by the upper limit when a difference between the reference level and the upper limit is less than a change in the cylinder pressure signal necessary to reflect a measured cylinder pressure increase. If the reference level reaches the upper limit, the cylinder pressure signal may be maintained at the upper limit.
Accordingly, the cylinder pressure signal (and therefore the reference level) is reset to a predetermined reset level from time to time. The cylinder pressure signal may be reset to the predetermined reset level by reducing an impedance at an input to the cylinder pressure sensor to effectively short circuit the output of the cylinder pressure sensor. A second electrical conductor may be used to coordinate the resetting between the cylinder pressure sensor and the control module. For example, the control module may transmit a reset signal to the cylinder pressure sensor via the second electrical wire to instruct the cylinder pressure sensor to reset the cylinder pressure signal to the predetermined reset level. For another example, the cylinder pressure sensor may transmit a reset signal to the control module via the second electrical wire to notify the control module that the cylinder pressure sensor is resetting the cylinder pressure signal to the predetermined reset level.